Capacitive sensor core with flexible hinge and sensor using the same

Abstract

A capacitive sensor core with flexible hinge includes a main grid plate, an auxiliary grid plate, and a mechanical structure transferring the measuring quantity to the displacement between the main grid plate and the auxiliary grid plate, the mechanical structure includes a stationary element and a moving element, the auxiliary grid plate and the main grid plate are fixed to the driven portion of the moving element and the corresponding position of the stationary element respectively, the stationary element and the moving element are connected through a flexible hinge; the flexible hinge consists of at least two supporting spring leafs, one end of each of the supporting spring leafs is connected to the stationary element, the other end is connected to the moving element; the plane of each of the supporting spring leafs is perpendicular to the planes of the main and auxiliary grid plates.

What is claimed is: 
     
       1. A capacitive sensor core with flexible hinge, comprising:
 a main grid plate; 
 a minor grid plate; and 
 a mechanism for converting a measurement to a relative displacement between the main grid plate and the minor grid plate; 
 wherein the mechanism comprises a stationary arm ( 1 ) and an active arm, the minor grid plate ( 4 ) and the main grid plate ( 3 ) are respectively mounted on a driven portion of the active arm and the stationary arm, the stationary arm is connected to the active arm by a flexible hinge; the flexible hinge comprises at least two supporting spring leaves ( 7 ), each supporting spring leaf ( 7 ) is connected to the stationary arm at one end, and the other end of the supporting spring leaf ( 7 ) is connected to the active arm; each supporting spring leaf ( 7 ) is vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); and 
 the flexible hinge between the active arm ( 2 ) and the stationary arm ( 1 ) comprises the intersected supporting spring leaves ( 7 ), the active arm ( 2 ) is rotated around the intersection of the supporting spring leaves ( 7 ) as the rotation center with respect to the stationary arm ( 1 ), the main grid plate ( 3 ) mounted on the stationary arm ( 1 ) and the minor grid plate ( 4 ) mounted on the driven portion of the active arm ( 2 ) are the main grid plate ( 3 ) and the minor grid plate ( 4 ) of a capacitive angular movement sensor; or 
 the flexible hinge between the active arm ( 2 ) and the stationary arm ( 1 ) comprises the supporting spring leaves ( 7 ) that are symmetrically arranged, the active arm ( 2 ) performs linear movement with respect to the stationary arm ( 1 ) according to the symmetry central line of the supporting spring leaves ( 7 ), the main grid plate ( 3 ) mounted on the stationary arm ( 1 ) and the minor grid plate ( 4 ) mounted on the driven portion of the active arm ( 2 ) are the main grid plate ( 3 ) and the minor grid plate ( 4 ) of a linear displacement capacitive sensor. 
 
     
     
       2. The capacitive sensor core with flexible hinge of  claim 1 , wherein the hinged portions of the active arm ( 2 ) and the stationary arm ( 1 ) are parallel with respect to each other in transverse direction, the minor grid plate ( 4 ) on the driven portion of the active arm ( 2 ) and the main grid plate ( 3 ) on the stationary arm ( 1 ) are parallel with respect to each other in longitudinal direction above the hinged portions of the active arm ( 2 ) and the stationary arm ( 1 ); straight slots in diagonal direction are provided on the lower front portion or upper front portion of the hinged portion of the stationary arm ( 1 ) and on the upper front portion or lower front portion of the active arm ( 2 ), and these two slots are vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); straight slots in diagonal direction are also provided on the lower back portion or upper back portion of the hinged portion of the stationary arm ( 1 ) and on the upper back portion or lower back portion of the hinged portion of the active arm ( 2 ), and these two slots are also vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); the two ends of a supporting spring leaf ( 7 ) are respectively inserted in the straight slot on the upper front portion or lower front portion of the hinged portion of the stationary arm ( 1 ) and the straight slot on the lower front portion or upper front portion of the hinged portion of the active arm ( 2 ); the two ends of another supporting spring leaf ( 7 ) are respectively inserted in the straight slot on the upper back portion or lower back portion of the hinged portion of the stationary arm ( 1 ) and the straight slot on the lower back portion or upper back portion of the hinged portion of the active arm ( 2 ); a line passing through the intersection point of the supporting spring leaves ( 7 ) and vertical to the main sensor grid plate ( 3 ) and minor sensor grid plate ( 4 ) is the virtual axis of rotation of the active arm ( 2 ) with respect to the stationary arm ( 1 ). 
     
     
       3. The capacitive sensor core with flexible hinge of  claim 2 , wherein the upper and lower ends of the hinged portion of the active arm ( 2 ) are both mounted with a horizontal pilot pin ( 8 ), these two horizontal pilot pins ( 8 ) are parallel and located in a longitudinal plane, and correspondingly pin holes for receiving the pilot pins ( 8 ) are provided on the hinged portion of the stationary arm ( 1 ). 
     
     
       4. The capacitive sensor core with flexible hinge of  claim 3 , wherein horizontal dynamometric springs ( 5 ) are connected between the stationary arm ( 1 ) and the active arm ( 2 ) at positions above and below the two pilot pins ( 8 ). 
     
     
       5. The capacitive sensor core with flexible hinge of  claim 1 , wherein the supporting spring leaf ( 7 ) is of an angled shape or arc shape, and located symmetrically on the two sides of the active arm. 
     
     
       6. The capacitive sensor core with flexible hinge of  claim 1 , wherein two pairs of the main grid plate ( 3 ) and the minor grid plate ( 4 ) are mounted on the stationary arm ( 1 ) and the active arm ( 2 ), one pair is the main grid plate and the minor grid plate of a calibration sensor, and ½ pitch of the calibration sensor is the measuring range, and the other pair is the main grid plate and the minor grid plate of a measuring sensor. 
     
     
       7. A capacitive angular movement sensor, comprising:
 a capacitive sensor core with flexible hinge, comprising a main grid plate ( 3 ), a minor grid plate ( 4 ) and a mechanism for converting a measurement to a relative movement between the main grid plate and the minor grid plate; 
 wherein the mechanism comprises a stationary arm and an active arm, the minor grid plate ( 4 ) and the main grid plate ( 3 ) are respectively mounted on a driven portion of the active arm and the stationary arm, the stationary arm is connected to the active arm by a flexible hinge; the active arm is mounted on the stationary arm via the flexible hinge that is used as supporting arm to form a lever-like mechanism, the active arm is rotated around the rotation center of the flexible hinge as the rotation center of the lever-like mechanism with respect to the stationary arm, the main grid plate ( 3 ) mounted on the stationary arm and the minor grid plate ( 4 ) mounted on the driven portion of the active arm are the main grid plate ( 3 ) and the minor grid plate ( 4 ) of a capacitive angular movement sensor, the flexible hinge comprises at least two supporting spring leaves ( 7 ), each supporting spring leaf ( 7 ) is connected to the stationary arm at one end, and the other end of the supporting spring leaf ( 7 ) is connected to the active arm; each supporting spring leaf ( 7 ) is vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ). 
 
     
     
       8. The capacitive angular movement sensor of  claim 7 , wherein the hinged portions of the active arm ( 2 ) and the stationary arm ( 1 ) are parallel with respect to each other in transverse direction, the minor grid plate ( 4 ) on the driven portion of the active arm ( 2 ) and the main grid plate ( 3 ) on the stationary arm ( 1 ) are parallel with respect to each other in longitudinal direction above the hinged portions of the active arm ( 2 ) and the stationary arm ( 1 ); straight slots in diagonal direction are provided on the upper front portion or lower front portion of the hinged portion of the stationary arm ( 1 ) and on the lower front portion or upper front portion of the active arm ( 2 ), and these two slots are vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); straight slots in diagonal direction are also provided on the lower back portion or upper back portion of the hinged portion of the stationary arm ( 1 ) and on the upper back portion or lower back portion of the hinged portion of the active arm ( 2 ), and these two slots are also vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); the two ends of a supporting spring leaf ( 7 ) are inserted in the straight slot on the upper front portion or lower front portion of the hinged portion of the stationary arm ( 1 ) and the straight slot on the lower front portion or upper front portion of the hinged portion of the active arm ( 2 ) respectively; the two ends of another supporting spring leaf ( 7 ) are inserted in the straight slot on the upper back portion or lower back portion of the hinged portion of the stationary arm ( 1 ) and the straight slot on the lower back portion or upper back portion of the hinged portion of the active arm ( 2 ) respectively; a line passing through the intersection point of the supporting spring leaves ( 7 ) and vertical to the main sensor grid plate ( 3 ) and minor sensor grid plate ( 4 ) is the virtual axis of rotation of the active arm ( 2 ) with respect to the stationary arm ( 1 ); a measuring arm inclined towards the stationary arm ( 1 ) is connected to the lower portion of the hinged portion of the active arm ( 2 ), a horizontal measuring pin ( 9 ) is located at the end of the measuring arm, the hinged portion of the stationary arm ( 1 ) is connected with a vertical supporting arm, a cam ( 12 ) is mounted on a cam shaft on the end of the vertical supporting arm, the cam shaft is parallel to the measuring pin ( 9 ), and the measuring pin ( 9 ) leans on the surface of the cam ( 12 ). 
     
     
       9. The capacitive angular movement sensor of  claim 8 , wherein the upper and lower ends of the hinged portion of the active arm ( 2 ) are both mounted with a horizontal pilot pin ( 8 ), these two horizontal pilot pins ( 8 ) are parallel and located in a longitudinal plane, and correspondingly pin holes for receiving the pilot pins ( 8 ) are provided on the hinged portion of the stationary arm ( 1 ). 
     
     
       10. The capacitive angular movement sensor of  claim 9 , wherein horizontal dynamometric springs ( 5 ) are connected between the stationary arm ( 1 ) and the active arm ( 2 ) at positions above and below the two pilot pins ( 8 ). 
     
     
       11. The capacitive angular movement sensor according to  claim 7 , wherein two pairs of the main grid plate ( 3 ) and the minor grid plate ( 4 ) are mounted on the stationary arm ( 1 ) and the active arm ( 2 ), one pair is the main grid plate and the minor grid plate of a calibration sensor, and ½ pitch of the calibration sensor is the measuring range, and the other pair is the main grid plate and the minor grid plate of a measuring sensor. 
     
     
       12. An adjustable digital caliper, comprising:
 a capacitive sensor core with flexible hinge, comprising a main grid plate ( 3 ), a minor grid plate ( 4 ) and a mechanism for converting a measurement to a relative movement between the main grid plate and the minor grid plate; 
 wherein the mechanism comprises a stationary arm and an active arm, the minor grid plate ( 4 ) and the main grid plate ( 3 ) are respectively mounted on a driven portion of the active arm and the stationary arm, the stationary arm is connected to the active arm by a flexible hinge; the flexible hinge comprises at least two supporting spring leaves ( 7 ), each supporting spring leaf ( 7 ) is connected to the stationary arm at one end, and the other end of the supporting spring leaf ( 7 ) is connected to the active arm; each supporting spring leaf ( 7 ) is vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); the flexible hinge between the active arm ( 2 ) and the stationary arm ( 1 ) comprises the intersected supporting spring leaves ( 7 ), the active arm ( 2 ) is rotated around the intersection of the supporting spring leaves ( 7 ) as the rotation center with respect to the stationary arm ( 1 ), the main grid plate ( 3 ) mounted on the stationary arm ( 1 ) and the minor grid plate ( 4 ) mounted on the driven portion of the active arm ( 2 ) are the main grid plate ( 3 ) and the minor grid plate ( 4 ) of a capacitive angular movement sensor. 
 
     
     
       13. The adjustable digital caliper of  claim 12 , wherein the hinged portions of the active arm ( 2 ) and the stationary arm ( 1 ) are parallel with respect to each other in transverse direction, the minor grid plate ( 4 ) on the driven portion of the active arm ( 2 ) and the main grid plate ( 3 ) on the stationary arm ( 1 ) are parallel with respect to each other in longitudinal direction above the hinged portions of the active arm ( 2 ) and the stationary arm ( 1 ); straight slots in diagonal direction are provided on the upper front portion or lower front portion of the hinged portion of the stationary arm ( 1 ) and on the lower front portion or upper front portion of the active arm ( 2 ), and these two slots are vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); straight slots in diagonal direction are also provided on the lower back portion or upper back portion of the hinged portion of the stationary arm ( 1 ) and on the upper back portion or lower back portion of the hinged portion of the active arm ( 2 ), and these two slots are also vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); the two ends of a supporting spring leaf ( 7 ) are inserted in the straight slot on the upper front portion or lower front portion of the hinged portion of the stationary arm ( 1 ) and the straight slot on the lower front portion or upper front portion of the hinged portion of the active arm ( 2 ) respectively; the two ends of another supporting spring leaf ( 7 ) are inserted in the straight slot on the upper back portion or lower back portion of the hinged portion of the stationary arm ( 1 ) and the straight slot on the lower back portion or upper back portion of the hinged portion of the active arm ( 2 ) respectively; a line passing through the intersection point of the supporting spring leaves ( 7 ) and vertical to the main sensor grid plate ( 3 ) and minor sensor grid plate ( 4 ) is the virtual axis of rotation of the active arm ( 2 ) with respect to the stationary arm ( 1 ); the lower portion of the hinged portion of the active arm is connected with a vertical active measuring arm, an open-bottom frame is arranged on the other side of the hinged portion of the stationary arm ( 1 ), two gliding guide bars ( 6 ) in parallel are provided in the rectangular frame, pilot holes for respectively receiving the gliding guide bars ( 6 ) are provided on the upper end of the vertical stationary measuring arm ( 17 ), a bolt for adjusting measuring range  11  is cooperated with the inner thread on the upper end of the stationary measuring arm ( 17 ), the bolt ( 11 ) is of self-locking function, the measuring surface on the lower end of the stationary measuring arm ( 17 ) faces and is parallel to the measuring surface on the lower end of the active measuring arm and is vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ). 
     
     
       14. The adjustable digital caliper of  claim 12 , wherein the upper end of the hinged portion and the lower end of the stationary arm ( 1 ) are provided with at least one horizontal pilot pin ( 8 ),the pilot pin ( 8 ) is inserted into a corresponding pin hole on the active arm ( 2 ). 
     
     
       15. The adjustable digital caliper of  claim 14 , wherein a dynamometric spring ( 5 ) is provided horizontally above the pilot pin ( 8 ) and below the main grid plate ( 3 ), the dynamometric spring ( 5 ) leans on the active arm ( 2 ). 
     
     
       16. The adjustable digital caliper of  claim 15 , wherein the active arm ( 2 ) is further mounted horizontally with a lifting screw ( 10 ) above the dynamometric spring  5  and below the minor grid plate ( 4 ). 
     
     
       17. The adjustable digital caliper of  claim 12 , wherein the measuring surface of the active measuring arm is further provided with a cylindrical measuring head  13  that is capable to swing slightly. 
     
     
       18. The adjustable digital caliper of  claim 12 , wherein two pairs of the main grid plate ( 3 ) and the minor grid plate ( 4 ) are mounted on the stationary arm ( 1 ) and the active arm ( 2 ), one pair is the main grid plate and the minor grid plate of a calibration sensor, and ½ pitch of the calibration sensor is the measuring range, and the other pair is the main grid plate and the minor grid plate of a measuring sensor. 
     
     
       19. A lever gauge, comprising:
 a capacitive sensor core with flexible hinge, comprising a main grid plate ( 3 ), a minor grid plate ( 4 ) and a mechanism for converting a measurement to a relative movement between the main grid plate and the minor grid plate; 
 wherein the mechanism comprises a stationary arm and an active arm, the minor grid plate ( 4 ) and the main grid plate ( 3 ) are respectively mounted on a driven portion of the active arm and the stationary arm, the stationary arm is connected to the active arm by a flexible hinge; the flexible hinge comprises at least two supporting spring leaves ( 7 ), each supporting spring leaf ( 7 ) is connected to the stationary arm at one end, and the other end of the supporting spring leaf ( 7 ) is connected to the active arm; each supporting spring leaf ( 7 ) is vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); the flexible hinge between the active arm ( 2 ) and the stationary arm ( 1 ) comprises the intersected supporting spring leaves ( 7 ), the active arm ( 2 ) is rotated around the intersection of the supporting spring leaves ( 7 ) as the rotation center with respect to the stationary arm ( 1 ), the main grid plate ( 3 ) mounted on the stationary arm ( 1 ) and the minor grid plate ( 4 ) mounted on the driven portion of the active arm ( 2 ) are the main grid plate ( 3 ) and the minor grid plate ( 4 ) of a capacitive angular movement sensor. 
 
     
     
       20. The lever gauge of  claim 19 , wherein the stationary arm is a stationary frame ( 1 - 1 ), the stationary frame ( 1 - 1 ) is disposed vertically, the active arm ( 2 ) is disposed vertically inside the stationary frame ( 1 - 1 ), the minor grid plate ( 4 ) mounted on the driven portion of the active arm ( 2 ) and the main grid plate ( 3 ) mounted in the stationary frame ( 1 - 1 ) are parallel in longitudinal direction; a seat ( 14 ) for the supporting spring leaf is provided on the lower end of the active arm ( 2 ) outside the stationary frame ( 1 - 1 ); an inclined straight slot is provided on the bottom of the stationary frame ( 1 - 1 ) on the left side of the opening, and an inclined straight slot is provided on the top left portion of the seat ( 14 ), and these two straight slots are vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); an inclined straight slot is provided on the bottom of the stationary frame ( 1 - 1 ) on the right side of the opening, and an inclined straight slot is provided on the top right portion of the seat ( 14 ), and these two straight slots are vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); the two ends of the two supporting spring leaves ( 7 ) are respectively inserted in the straight slots on the stationary frame ( 1 - 1 ) and the straight slots on the seat ( 14 ), the obliquity of the two supporting spring leaves ( 7 ) which intersect inside the seat ( 14 ) is identical, and the intersecting line of the two supporting spring leaves ( 7 ) is vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ) and is the virtual rotation axis of the active arm ( 2 ) with respect to the stationary frame ( 1 - 1 ); the seat ( 14 ) is further hinged with a base ( 15 ) for the measuring head, the bottom of the base ( 15 ) is connected to the measuring stick ( 16 ) having a spherical head. 
     
     
       21. The lever gauge of  claim 20 , wherein the base ( 15 ) is hinged to the seat ( 14 ). 
     
     
       22. The lever gauge of  claim 21 , wherein an orientation wheel ( 18 ) for the active arm is mounted in the stationary frame ( 1 - 1 ), the orientation wheel ( 8 ) is of a groove for movably receiving the active arm ( 2 ), the direction of the groove on the orientation wheel ( 8 ) is the same as the swinging direction of the active arm ( 2 ). 
     
     
       23. The lever gauge of  claim 22 , wherein a pressing plate ( 19 ) that is rotated around a shaft is further mounted inside the stationary frame ( 1 - 1 ), a pin ( 20 ) on the upper end of the pressing plate ( 19 ) and a pin ( 20 ) on the lower end of the pressing plate ( 19 ) lean on the two sides of the active arm ( 2 ) respectively, an end of a measuring spring ( 5 ) is connected to the pin ( 20 ) on one side of the active arm ( 2 ), and the other end of the measuring spring ( 5 ) is connected to the inner surface of the stationary frame ( 1 - 1 ) on the other side of the active arm ( 2 ). 
     
     
       24. The lever gauge of  claim 23 , wherein positioning cams ( 21 ) at an upper left position and another lower right position are arranged respectively on the two sides of the longitudinal portion of the active arm ( 2 ), and contacted with the outer edge of the pressing plate ( 19 ). 
     
     
       25. The lever gauge of  claim 19 , wherein two pairs of the main grid plate and the minor grid plate are mounted on the stationary arm and the active arm, one pair is the main grid plate and the minor grid plate of a calibration sensor, and ½ pitch of the calibration sensor is the measuring range, and the other pair is the main grid plate and the minor grid plate of a measuring sensor. 
     
     
       26. A micrometer, comprising:
 a capacitive sensor core with flexible hinge, comprising a main grid plate ( 3 ), a minor grid plate ( 4 ) and a mechanism for converting a measurement to a relative movement between the main grid plate and the minor grid plate; 
 wherein the mechanism comprises a stationary arm and an active arm, the minor grid plate ( 4 ) and the main grid plate ( 3 ) are respectively mounted on a driven portion of the active arm and the stationary arm, the stationary arm is connected to the active arm by a flexible hinge; the flexible hinge comprises at least two supporting spring leaves ( 7 ), each supporting spring leaf ( 7 ) is connected to the stationary arm at one end, and the other end of the supporting spring leaf ( 7 ) is connected to the active arm; each supporting spring leaf ( 7 ) is vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); the flexible hinge between the active arm ( 2 ) and the stationary arm ( 1 ) comprises the supporting spring leaves ( 7 ) that are symmetrically arranged, the active arm ( 2 ) performs linear movement with respect to the stationary arm ( 1 ) according to the symmetry central line of the supporting spring leaves ( 7 ), the main grid plate ( 3 ) and the minor grid plate ( 4 ) respectively mounted on the stationary arm and the active arm are the main grid plate ( 3 ) and the minor grid plate ( 4 ) of a linear displacement capacitive sensor. 
 
     
     
       27. The micrometer of  claim 26 , wherein the supporting spring leaf ( 7 ) is of an angled shape or arc shape, and located symmetrically on the two sides of the active device. 
     
     
       28. The micrometer of  claim 27 , wherein the stationary arm is a circular casing ( 1 - 2 ), the main grid plate ( 3 ) is mounted in the center of the circular casing ( 1 - 2 ), the bottom of the circular casing ( 1 - 2 ) behind the main grid plate ( 3 ) is mounted with a vertical guide sleeve, the pilot pin ( 22 ) is received in the guide sleeve and the two ends of the pilot pin ( 22 ) are exposed out of the guide sleeve, the active device is connected to the stationary device via the flexible hinge, the pilot pin ( 22 ) and the guide sleeve form a guide device which performs linear movement with respect to the circular casing ( 1 - 2 ) according to the symmetry central line of the flexible hinge, the front surface of the main grid plate ( 3 ) is mounted with the vertical active arm ( 2 ), a minor grid plate  4  is mounted on a surface of the active arm ( 2 ) facing the main grid plate ( 3 ), the upper end of the active arm ( 2 ) is connected to the upper end of the pilot pin ( 22 ) via transverse connecting element; a straight slot inclined towards the bottom left side is provided on the left side of the body below the main grid plate ( 3 ), a straight slot inclined towards the bottom right side from outside to inside is provided on the right side of the body below the main grid plate ( 3 ); a straight slot inclined towards the top right side is provided on the left side of the connecting element, a straight slot inclined towards the top left side is provided on the right side of the connecting piece, all the straight slots are vertical to the main grid plate ( 3 ) and the minor grid plate ( 4 ); angled supporting spring leaves ( 7 ) are provided on the two sides of the main grid plate ( 3 ), the two ends of each supporting spring leaf ( 7 ) are inserted to the straight slots on the connecting element and the main grid plate ( 3 ) on the same side, the two supporting spring leaves ( 7 ) form a rhombus, the lower end of the active arm ( 2 ) is connected vertically with a measuring stick ( 16 ), and the measuring stick ( 16 ) extends through a mounting hole on the bottom of the circular casing ( 1 - 2 ) and is exposed out of the circular casing ( 1 - 2 ), and the measuring stick ( 16 ) has a tapered measuring head on the end. 
     
     
       29. The micrometer of  claim 28 , wherein each supporting spring leaf ( 7 ) is broken at the folded position where a left sliding piece ( 23 ) and a right sliding piece ( 23 ) are arranged, the supporting spring leaves ( 7 ) are received in the straight slots on the left and right sliding pieces. 
     
     
       30. The micrometer of  claim 29 , wherein a lower sleeve ( 24 ) is mounted on the measuring stick ( 16 ), the upper end of the lower sleeve ( 24 ) is mounted in the mounting hole on the bottom of the circular casing ( 1 - 2 ). 
     
     
       31. The micrometer of  claim 26 , wherein two pairs of the main grid plate ( 3 ) and the minor grid plate ( 4 ) are mounted on the stationary arm ( 1 ) and the active arm ( 2 ), one pair is the main grid plate and the minor grid plate of a calibration sensor, and ½ pitch of the calibration sensor is the measuring range, and the other pair is the main grid plate and the minor grid plate of a measuring sensor.